Gas Flow in Pipe from Detonation Cord Pressure Source

[dank_]

This is my first post.. so here goes!

I have an application where I'd like to understand pressure drop in a length of tube that's open at both ends. The initial pressure is from a linear explosive so it's basically very high pressure combustion products instantaneously generated along the entire length of the tube. My goal is just to get an order of magnitude answer on when my interior pressure will drop to near atmospheric. I have tools to give me initial conditions of the tube immediately after detonation.

Any thoughts on how to bound the timescale on which pressure will drop or, better yet, solve for pressure over time? Are the assumptions of choked flow applicable with no choking orifice? Do Fanno flow assumptions work to bound the problem even though it's a very short transient?

 

[LittleInch]

I hate to see no response so here goes.

So how long is the tube?

Any explosion pressure wave will travel at the speed of sound of the gas.
I think you're into choked flow for the pipe / tube diameter.

How big an order of magnitude?

If it's something like a gun barrel length then I would go for about 1 -2 seconds.

This is a very high speed transient event so would need some sort of modelling in microseconds.

Some back ground to this and why you want to know would help a lot.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

There should be papers out there from guys that do explosive welding and forming of tubes.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[hydtools]

Maybe something like the blowdown equation:

https://www.vanec.com/pressurized-volume-blowdown-time-calculation.html

Ted